DE112020004109T5 - Methods and systems for semiconductor metrology based on soft X-ray reflectometry with wavelength resolution - Google Patents

Abstract

Methods and systems for measuring structural and material properties of semiconductor structures based on wavelength-resolved soft X-ray reflectometry (WR-SXR) at several diffraction orders are presented. WR-SXR measurements are simultaneous high-throughput measurements over several diffraction orders with a large spectral width. The availability of wavelength-resolved signal information at each of the multiple diffraction orders improves measurement accuracy and throughput. Each non-zero diffraction order contains multiple measurement points, each different measurement point being associated with a different wavelength. In some embodiments, WR-SXR measurements are performed with X-ray energy in a range of 10-5,000 electron volts at grazing angles of incidence in a range of 1-45 degrees. In some embodiments, the illumination beam is steered to have relatively high divergence in one direction and relatively low divergence in a second direction orthogonal to the first direction. In some embodiments, multiple detectors are used, each detecting different diffraction orders.

Description

TECHNICAL AREA

The described embodiments relate to x-ray metrology systems and methods, and more particularly to methods and systems for improved measurement accuracy.

BACKGROUND INFORMATION

Semiconductor devices such as logic and memory devices are typically fabricated through a series of processing steps applied to a sample. The various features and multiple structural levels of the semiconductor devices are formed through these processing steps. For example, lithography is one semiconductor manufacturing process among others that involves creating a pattern on a semiconductor wafer. Additional examples of semiconductor fabrication processes include, but are not limited to, chemical mechanical polishing, etching, deposition, and ion implantation. Multiple semiconductor devices can be fabricated on a single semiconductor wafer and then separated into individual semiconductor devices.

Metrology processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to achieve higher yields. A number of metrology-based techniques, including implementations of scatterometry and reflectometry and associated analysis algorithms, are commonly used to characterize critical dimensions, layer thicknesses, composition and other parameters of nanoscale structures.

Conventionally, critical dimension scatterometry measurements are performed on targets composed of thin layers and/or repeating periodic structures. During device fabrication, these layers and periodic structures typically represent the actual device geometry and material structure or an intermediate design. As devices (e.g., logic and memory devices) move toward smaller, nanometer-scale dimensions, characterization becomes more difficult. Devices with complex three-dimensional geometry and materials with different physical properties add to the difficulty of characterization.

Accurate information about the material composition and shape of nanostructures is limited in the process development environment of a state-of-the-art front-end semiconductor fabrication facility. Scatterometric optical metrology systems rely on accurate geometric and dispersion models to avoid measurement errors. With limited a priori knowledge about the material composition and shape of nanostructures, the development and validation of measurement recipes is a slow and tedious process. For example, cross-sectional transmission electron microscopy (TEM) images are used to guide the development of optical scatterometry models, but TEM imaging is slow and destructive.

Scatterometric optical metrology instruments, using infrared to visible light, measure zero-order diffraction signals from sub-wavelength structures. As the critical dimensions of devices continue to shrink, the sensitivity and performance of scatterometric optical metrology decreases. When absorbing materials are present in the structure to be measured, penetration and scattering of illuminating light in the optical range (e.g. 0.5 - 10 eV) limit the usefulness of conventional optical metrology systems.

Similarly, electron beam based metrology systems have difficulty penetrating semiconductor structures due to absorption and scattering of the illuminating, backscattered, and secondary emission electrons.

Atomic force microscopes (AFM) and scanning tunneling microscopes (STM) are capable of atomic resolution, but they can only scan the surface of the sample. In addition, AFM and STM microscopes require long scan times that make these technologies impractical in high volume manufacturing (HVM).

Transmission small-angle X-ray scatterometry (T-SAXS) systems using photons at a hard X-ray energy level (>15 keV) have shown promise for sophisticated mes sapplications proven. Various aspects of the application of SAXS technology to the measurement of critical dimensions (CD-SAXS) and overlay (OVL-SAXS) are described in 1) U.S. Patent No. 7,929,667 by Zhuang and Fielden entitled "High-brightness X-ray metrology", 2) US Patent Publication No. 2014/0019097 by Bakeman, Shchegrov, Zhao and Tan entitled "Model Building And Analysis Engine For Combined X-ray And Optical Metrology”, 3) US Patent Publication No. 2015/0117610 by Veldman, Bakeman, Shchegrov and Mieher entitled “Methods and Apparatus For Measuring Semiconductor Device Overlay Using X-ray Metrology”, 4) US Patent Publication No. 2016/0202193 by Hench, Shchegrov and Bakeman, entitled "Measurement System Optimization For X-ray Based Metrology", 5) US Patent Publication No. 2017/0167862 by Dziura, Gellineau and Shchegrov entitled "X-ray Metrology For High Aspect Ratio Structures" and 6) US Patent Publication No. 2018/0106735 by Gellineau, Dziura, Hench, Veldman and Zalubovsky entitled "Full Beam Metrology for X-ray Scatterometry Systems". The above patent documents are assigned to KLA-Tencor Corporation of Milpitas, California (USA), the contents of each of which are hereby incorporated by reference in their entirety.

SAXS has also been used in materials characterization and other non-semiconductor related applications. Exemplary systems have been commercialized by several companies, including Xenocs SAS (www.xenocs.com), Bruker Corporation (www.bruker.com), and Rigaku Corporation (www.rigaku.com/en).

Research on CD-SAXS metrology of semiconductor structures is also described in the scientific literature. Most research groups have used high brightness X-ray synchrotron sources, which are not suitable for use in a semiconductor fab because of their immense size, cost, etc. An example of such a system is given in the article entitled "Intercomparison between optical and X-ray Scatterometry Measurements of FinFET Structures" by Lemaillet, Germer, Kline et al., Proc. SPIE, v.8681, p. 86810Q (2013). More recently, a group at the National Institute of Standards and Technology (NIST) has initiated research using compact and bright X-ray sources similar to those used in the U.S. Patent No. 7,929,667 are described. This research is described in an article entitled "X-ray scattering critical dimensional metrology using a compact X-ray source for next generation semiconductor devices", J. Micro/Nanolith. MEMS MOEMS 16(1), 014001 (Jan-Mar 2017).

The scattering of hard X-rays from flat structures, e.g. B. Applications in logic metrology, however, is weak, which severely limits the achievable measurement resolution and throughput. Therefore, T-SAXS has not proven to be a viable option for logic metrology applications in an HVM environment.

T-SAXS systems achieve a small beam area on the wafer due to the near-normal incidence illumination. However, T-SAXS systems require high energy photons (e.g. >16 keV) for adequate transmission through a wafer to be measured. Typically, the diffraction efficiency scales with photon energy E by 1/E ² , and the angular separation of the diffraction orders scales by 1/E. To avoid order overlaps for a 2D periodic structure, the solid angle acceptance scales with 1/E ² . These scaling factors place a severe disadvantage on T-SAXS systems for flat structure metrology.

In addition, in a transmission measurement, the diffraction images from all previous structuring steps are superimposed on the diffraction image of the current layer structure. Since the minimum pitch (i.e. period) of critical metal layers is expected to converge to values differing by only 10-20%, the angular acceptance is severely limited to separate diffraction signals at the detector. Otherwise, the geometric information of all previous layers must be passed to the metrology system characterizing the current layer. Typically, in the context of a complex HVM environment, it is very difficult to obtain and manage the required metrology and process information.

Conventional GI-SAXS systems operate near the critical angles for reflection (e.g., grazing angles less than one degree) for semiconductor materials and photon energies above 8 keV to maximize diffracted intensity. This results in an extremely large spot size of the illumination beam projected onto the wafer (e.g., greater than 1mm). This is so large that even metrology targets in scribe lines are useless. Therefore, extremely large, specialized metrology targets must be created on the wafer to perform GI-SAXS measurements. This loss of wafer area for functions is costly. In addition, the surface sensitivity of GI-SAXS measurements is excellent, however, penetration of high aspect ratio structures is very limited due to evanescent field behavior.

US Patent Publication No. 2017/0357155A1 by Quintanilha et al. entitled "Metrology Methods, Metrology Apparatus, and Device Manufacturing Method" describes a system that uses a spectrometer-type detector to produce a wavelength-resolved signal in the 0th order. This approach requires the use of a diffraction element (e.g., a diffraction grating) in the collection path between the wafer and the light sensitive detection elements to separate signals of different wavelengths. This limits the types of detectors that can be used to make the spectral measurements.

In summary, there is a need for a dimensional metrology system with metrology capability for both low and high aspect ratio structures and an illumination beam spot size that is compatible with scribe line targets. In one example, there is a need for a metrology system to estimate shape and edge placement parameters of high aspect ratio (HAR) structures at HVM throughputs. Furthermore, it should be possible to develop and validate measurement recipes for the metrology system and to operate the metrology system in a high volume manufacturing (HVM) environment without substantial a priori information on dimensions and material composition.

OVERVIEW

Methods and systems for measuring structural and material properties of semiconductor structures based on wavelength-resolved soft X-ray reflectometry (WR-SXR) at several diffraction orders are presented here. The methods and systems described herein provide simultaneous high-throughput measurements across multiple diffraction orders with large spectral width. The availability of wavelength-resolved signal information at each of the multiple diffraction orders improves measurement accuracy and throughput.

In general, WR-SXR measurements of a semiconductor wafer are made over a range of wavelengths, angles of incidence, and azimuth angles with a small beam spot size. In one aspect, the WR-SXR measurements are performed using soft X-ray (SXR) X-rays (i.e., 10-5,000 eV) at grazing incidence angles in the 1-45 degree range.

In general, the reflected zero-order beam will have a divergence similar to the divergence of the incident illuminating beam. Radiation scattered in non-zero diffraction orders will have a higher divergence than the incident illuminating beam because the incident illuminating beam contains multiple wavelengths, each diffracted at a slightly different angle within each of the non-zero diffractive orders. The angle of reflection for non-zero diffraction orders depends on the wavelength of the incident illuminating beam. For an incident illumination beam with multiple discrete illumination wavelengths, the scattered light includes multiple angles of reflection within each non-zero diffraction order. Similarly, for an incident illuminating beam with a continuous broadband spectrum, the scattered light contains a continuous spatial spreading of the reflected light as it strikes the detector within each non-zero diffraction order. Therefore, each non-zero diffraction order contains multiple measurement points, each different measurement point being associated with a different wavelength. Thus, each non-zero diffraction order contains a wavelength-resolved spectrum. In this way, a WR-SXR metrology system provides wavelength-resolved signal information without using a diffractive optical element in the optical path between the DUT and the detector.

A WR-SXR system is used to determine properties of a sample (eg, structural parameter values) based on wavelength-resolved signal information at one or more non-zero diffraction orders of scattered light.

In one aspect, the distance between the detector and the wafer to be measured is actively adjusted to change the resolution of the spectral information collected at the detector.

In another further aspect, focusing optics collect source emission and select one or more discrete wavelengths or spectral bands and focus the selected light onto a sample at grazing angles of incidence ranging from 1 to 45 degrees.

In another further aspect, the wavelength ranges, AOI, azimuth or any combination thereof projected onto the same measurement area are adjusted by actively positioning one or more mirror elements of the focusing optics.

In another aspect, a WR-SXR metrology system includes one or more beam slots or apertures to shape the illumination beam incident on a sample and selectively block a portion of the illumination light that would otherwise illuminate a metrology target under measurement. One or more beam slots define the beam size and beam shape such that the X-ray illumination spot fits within the area of the metrology target to be measured. In addition, one or more beam slits define the divergence of the illumination beam to limit the overlap of diffraction orders on the detector.

In another further aspect, a WR-SXR metrology system uses one or more mechanisms to control illumination beam energy. In general, illumination beam energies are selected to ensure sufficient x-ray penetration into the particular sample being measured.

In another further aspect, the incident illumination beam of a WR-SXR metrology system is controlled to have relatively high divergence in a direction transverse to the incident illumination beam and relatively low divergence in a second direction transverse to the incident illumination beam orthogonal to the first direction. In this way, the spatial spread across the active surface of the detector in the high divergence direction is orthogonal to the spatial spread across the active surface of the detector in the low divergence direction. The spatial spread over the active area of the detector in the direction of high divergence is dominated by the angle of incidence due to the relatively high divergence. In contrast, the spatial spread across the active surface of the detector in the direction of low divergence is dominated by the wavelength dispersion within each diffraction order, as described above. In this way, each non-zero diffraction order contains signal information about the structure to be measured due to the spectral reflectance (in the direction of low divergence) and the angular reflectance (in the direction of high divergence).

In another further aspect, measurement performance is improved by flowing one or more liquid materials or one or more gaseous materials onto the target to be measured to increase the contrast between the measured materials.

In another further aspect, a WR-SXR metrology system uses multiple detectors. In some embodiments, one or more diffraction orders are collected by a first detector and other diffraction orders are collected by another detector.

In another further aspect, the position of a detector of a WR-SXR metrology system is actively controlled to detect radiation reflected from the measured target.

The foregoing is an overview and therefore necessarily contains simplifications, generalizations and omissions of detail; consequently, those skilled in the art will recognize that the overview is illustrative only and is not in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein will become apparent in the non-limiting detailed description provided herein.

character list

• 1 FIG. 12 shows an illustration of a metrology device based on wavelength-resolved soft X-ray reflectometry (WR-SXR) for measuring properties of a sample, in one embodiment.
• 2 12 shows a representation of radiation scattered from a periodic target and detected by a detector of a WR-SXR metrology system in one embodiment.
• 3 FIG. 12 shows an illustration of radiation scattered from a periodic target and detected by a detector of a WR-SXR metrology system in another embodiment.
• 4 FIG. 12 shows a representation of an illumination beam incident on a wafer with a particular orientation described by an incidence angle θ and an azimuth angle Φ.
• 5 shows a representation of a portion of the scattered radiation incident on the active surface of the in 3 shown detector.
• 6 Figure 12 shows a plot of part of the scattered radiation incident on the active surface of a detector in another example.
• 7 Figure 12 shows an illustration of a WR-SXR metrology system for measuring properties of a sample in another embodiment.
• 8th FIG. 12 is an illustration of an illumination beam of a WR-SXR metrology system passing through a beam energy filter in one embodiment.
• 9 FIG. 12 is a graph showing the transmission curve of a beam energy filter made from layers of boron and tin about 0.2 microns thick deposited on a Kapton substrate.
• 10 Figure 12 shows an illustration of a WR-SXR metrology system for measuring properties of a sample in another embodiment.
• 11 shows a representation of scattered radiation incident on the active surface of the in 10 detector shown, for illuminating light with a single wavelength.
• 12 shows a representation of scattered radiation 118 incident on the active surface of the in 10 shown detector incident, for broadband illumination light.
• 13 FIG. 12 shows a graph illustrating the reflectivity of an Nb ₂ O ₅ mirror as a function of illumination beam energy.
• 14 Figure 12 shows an illustration of a WR-SXR metrology system for measuring properties of a sample, in another embodiment.
• 15 Figure 12 is a diagram illustrating an example modeling and analysis engine implemented by a computer system of a WR-SXR metrology system.
• 16A 12 is a diagram illustrating a periodic metrology target in an example.
• 16B Figure 12 is a diagram illustrating a decimated metrology target in an example.
• 17 12 is a flow chart illustrating a method for performing wavelength-resolved soft X-ray reflectometry (WR-SXR) measurements on a sample in one example.

DETAILED DESCRIPTION

Reference will now be made in detail to examples of background and some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Methods and systems for measuring structural and material properties (e.g. material composition, dimensional properties of structures and layers, etc.) of semiconductor structures associated with various semiconductor manufacturing processes based on X-ray illumination are presented. In particular, methods and systems for performing measurements of semiconductor structures based on wavelength-resolved soft X-ray reflectometry (WR-SXR) at multiple diffraction orders are presented here. The methods and systems described herein provide simultaneous high-throughput measurements across multiple diffraction orders with large spectral width. The availability of wavelength-resolved signal information at each of the multiple diffraction orders improves measurement accuracy and throughput.

Generally, WR-SXR measurements of a semiconductor wafer are made over a range of wavelengths, angles of incidence, and azimuth angles with a small beam spot size (e.g., less than 50 microns effective illumination spot diameter). In one aspect, the WR-SXR measurements are performed using soft X-ray (SXR) X-rays (i.e., 10-5,000 eV) at grazing incidence angles in the 1-45 degree range. Grazing angles for a particular measurement application are selected to achieve a desired penetration into the structure to be measured and to maximize measurement information content with a small beam spot size (e.g., less than 50 microns).

1 FIG. 11 illustrates an embodiment of a WR-SXR metrology tool 100 for measuring properties of a sample in at least one novel aspect. As in 1 shown, the sys tem 100 can be used to perform WR-SXR measurements over a measurement range that includes a periodic target 102 placed on a sample 101.

The illumination source 110 generates illumination radiation at multiple wavelengths. in the in 1 In the embodiment shown, illumination source 110 produces broadband illumination directed at a grazing angle G onto a periodic target 102 (e.g., a periodic grating) disposed on sample 101 . in the in 1 In the embodiment shown, the periodic target 102 is periodic in one direction (ie, the horizontal direction across the drawing). The periodic target extends uniformly with no periodicity in the orthogonal direction (ie, the direction perpendicular to the drawing sheet). 1 Figure 12 shows, by way of non-limiting example, a periodic target with periodicity in one direction. In general, the metrology methods and systems described herein are applicable to the measurement of periodic targets with periodicity in two directions (e.g., two orthogonal directions).

in the in 1 In the embodiment shown, illumination source 110 is a High Harmonic Generation (HHG) laser illumination source with a small illumination source area (less than 50 microns). In one example, the HHG laser illumination source 110 produces an illumination beam 114 with low beam divergence (e.g., less than 1 milliradian) in two orthogonal directions across the beam. Illumination beam 114 is projected onto periodic target 102 and in response radiation 118 is scattered by periodic target 102 and detected by detector 119 .

2 Figure 12 shows radiation 118 scattered by periodic target 102 and detected by detector 119 in more detail. As in 2 As shown, the wavelength spectrum 152 of the illumination beam 114 includes a number of discrete wavelengths. Stray radiation 118 includes radiation scattered by periodic target 102 into different diffraction orders. The reflected ray 118A is the zeroth order reflection from the periodic target 102. The diffracted radiation 118B corresponds to the +1 diffraction order. The diffracted radiation 118C corresponds to the diffraction order -1. The diffracted radiation 118D corresponds to the diffraction order +2. The diffracted radiation 118E corresponds to the diffraction order -2. The diffracted radiation 118F (not shown) corresponds to the +3 diffraction order. The diffracted radiation 118G (not shown) corresponds to the diffraction order -3. The diffracted radiation 118H (not shown) corresponds to the +4 diffraction order. The diffracted radiation 1181 (not shown) corresponds to the diffraction order -4. As in 2 As shown, each discrete wavelength present in the illumination beam is diffracted by the periodic target 102 at a different angle within each of the non-zero diffraction orders.

wobei λ die Wellenlänge des einfallenden Beleuchtungsstrahls ist, d die Gitterperiode, a die Beugungsordnung, Θ₀ der Einfallswinkel und Θ_a der Winkel des gebeugten Lichts. Der nominale Einfallswinkel (dargestellt als Winkel G in 1) ist jeder geeignete streifende Einfallswinkel (d. h. Winkel zwischen der Waferebene und dem einfallenden Beleuchtungsstrahl) zwischen 1 Grad und 45 Grad.In general, the zero order beam 118A will have a divergence similar to the divergence of the incident illumination beam 114 . The portions of the stray radiation 118 that scatter into non-zero diffraction orders have a higher divergence than the incident illumination beam 114 because the incident illumination beam 114 comprises multiple wavelengths, each diffracted at a slightly different angle within each of the non-zero diffraction orders . In general, the reflected angles are given by the grating equation (1); $$\text{a*}\mathrm{\lambda =}\text{d*}\left[\text{sin}\left({\mathrm{\theta }}_0\right)+\text{sin}\left({\mathrm{\theta }}_{\text{a}}\right)\right]$$

where λ is the wavelength of the incident illuminating beam, d is the grating period, a is the diffraction order, Θ ₀ is the angle of incidence and Θ _a is the angle of the diffracted light. The nominal angle of incidence (represented as angle G in 1 ) any suitable grazing incidence angle (ie, angle between the wafer plane and the incident illumination beam) is between 1 degree and 45 degrees.

As illustrated by Equation (1), the angle of reflection associated with the 0th diffraction order (a=0) is equal to the angle of incidence, regardless of wavelength. However, the angle of reflection for non-zero diffraction orders (a≠0) depends on the wavelength of the incident illuminating beam. For an incident illumination beam with multiple discrete illumination wavelengths, the scattered light includes multiple angles of reflection within each non-zero diffraction order. Similarly, for an incident illuminating beam with a continuous broadband spectrum, the scattered light contains a continuous spatial spread of the reflected light upon striking the detector 119 within each non-zero diffraction order.

As in 2 As shown, the wavelength spectrum 152 of the illumination beam 114 comprises four discrete wavelengths, and each non-zero diffraction order comprises each of the four discrete wavelengths lengths incident on the detector 119 at various locations. In this way, the detector 119 clearly resolves radiation scattered from the periodic target 102 at every discrete wavelength within every non-zero diffraction order. Measurements performed with multiple discrete illumination wavelengths may be preferred in certain measurement applications, e.g. B. when measuring 3D grids.

As in 3 As shown, the wavelength spectrum 155 of illumination beam 114 comprises a continuous broadband spectrum, and the scattered light within each non-zero diffraction order comprises continuous spatial spreading of the reflected light at detector 119 within each non-zero diffraction order. Each different wavelength of reflected light is incident on detector 119 at different locations within each non-zero diffraction order. In this way, the detector 119 clearly resolves radiation scattered from the periodic target 102 at each different wavelength within each non-zero diffraction order.

As in the 2 and 3 1, each non-zero diffraction order contains different reflected wavelengths landing at different locations on the photosensitive surface of detector 119. Thus, each non-zero diffraction order contains multiple measurement points, each different measurement point being associated with a different wavelength. Thus, each non-zero diffraction order contains a wavelength-resolved spectrum. In this way, the WR-SXR metrology system provides wavelength-resolved signal information without using a diffractive optical element in the optical path between the target to be measured and the detector. The detection of the spatial spread of each diffraction order according to the wavelength at the surface of the detector provides useful and unique information about the measured structure of interest and further improves the measurement performance.

Each orientation of the incident illumination beam 114 relative to the surface normal of a semiconductor wafer 101 is described by any two angular rotations of the wafer 101 in relation to the illumination beam 114 or vice versa. In one example, the orientation may be described in terms of a coordinate system affixed to the wafer. 4 Figure 12 depicts the illumination ray 114 incident on the wafer 101 with a particular orientation described by an incidence angle θ and an azimuth angle Φ. The XYZ coordinate system is affixed to the metrology system (e.g., illumination beam 114) and the X'Y'Z' coordinate system is affixed to the wafer 101. The Y-axis is aligned in a plane with the wafer 101 surface. X and Z are not aligned with the wafer 101 surface. Z' is aligned on an axis perpendicular to the wafer 101 surface, and X' and Y' lie in a plane aligned with the wafer 101 surface. As in 4 As shown, the X-ray illumination beam 114 is aligned with the Z-axis and thus lies within the XZ plane. The angle of incidence θ describes the orientation of the X-ray illumination beam 114 with respect to the surface normal of the wafer in the XZ plane. In addition, the azimuth angle Φ describes the orientation of the XZ plane with respect to the X'Z' plane. Together, θ and Φ uniquely define the orientation of the X-ray illumination beam 114 with respect to the wafer 101 surface. In this example, the orientation of the X-ray illumination beam with respect to the wafer 101 surface is given by a rotation about an axis perpendicular to the wafer 101 surface (ie, Z' -axis) and a rotation about an axis aligned in the surface of the wafer 101 (ie Y-axis). In some other examples, the orientation of the X-ray illumination beam with respect to the surface of the wafer 101 is achieved by rotation about a first axis aligned with the surface of the wafer 101 and another axis aligned with the surface of the wafer 101 and perpendicular to the first axis is described.

In the in the 2 and 3 In the examples shown, the azimuth angle is such that the incident illumination beam 114 illuminates the periodic target 102 in a direction that is aligned with the periodicity direction of the periodic target 102 (the horizontal direction across the drawing sheet) and is orthogonal to the direction of uniform expansion of the periodic target (direction perpendicular to the drawing sheet). 5 11 shows part of the scattered radiation 118 incident on the active surface of the detector 119, as described in FIGS 3 lighting conditions shown. More precisely shows 5 the reflected beam 118A of the 0th order, the diffracted radiation 118C corresponding to the diffraction order -1, the diffracted radiation 118E corresponding to the diffraction order -2 and the diffracted radiation 118G corresponding to the diffraction order -3. As in 5 As shown, each wavelength present in the illuminating beam is diffracted by the periodic target 102 at a different angle within each of the non-zero diffraction orders. Thus, the wavelength range λ _RANGE , which is im Illumination beam 114 is present, spatially spread in the y-direction for each of the non-zero diffraction orders.

In another example, the azimuth angle is such that the incident illumination beam 114 illuminates the periodic target 102 in a direction that is in the direction of uniform expansion of the periodic target (the direction perpendicular to the drawing sheet of FIG 3 ) is aligned and orthogonal to the periodicity direction of the periodic target 102 (the horizontal direction across the plot of FIG 3 ). 6 represents a portion of the scattered radiation 118 incident on the active surface of the detector 119 as measured under these illumination conditions. More precisely shows 6 the reflected beam 118A of the 0th order, the diffracted radiation 118B and 118C corresponding to the diffraction orders +1 and -1, respectively, the diffracted radiation 118D and 118E corresponding to the diffraction orders +2 and -2, respectively, and the diffracted radiation 118F and 118G corresponding to Figs Diffraction orders +3 and -3, respectively. As in 6 As shown, each wavelength present in the illuminating beam is diffracted by the periodic target 102 at a different angle within each of the non-zero diffraction orders. Thus, the wavelength range λ _RANGE present in illumination beam 114 is spatially spread across the active surface of detector 119 along arc 149 for each of the non-zero diffraction orders.

In another aspect, the distance between the detector and the wafer to be measured is actively adjusted to change the resolution of the spectral information collected at the detector. In some embodiments, an actuator (not shown) is configured to move detector 119 in response to a control command (not shown) communicated from computer system 130 to the actuator. Moving the detector away from the wafer to be measured increases the resolution of the collected spectral information, i.e. increasing spatial separation between any two different wavelengths at the detector with increasing distance. Conversely, moving the detector towards the wafer to be measured reduces the resolution of the collected spectral information, i. H. the spatial separation between any two different wavelengths at the detector decreases with decreasing distance.

The X-ray illumination source 110 is configured to generate SXR radiation suitable for WR-SXR measurements. The x-ray illumination source 110 is a high brightness, high etendue polychromatic source. In some embodiments, x-ray illumination source 110 is configured to generate x-ray radiation in a range between 10-5,000 electron volts. In general, any suitable high-brightness X-ray illumination source capable of producing high-brightness SXR at sufficient flux levels to enable high-throughput in-line metrology can be considered to provide X-ray illumination for WR-SXR measurements. Some examples of suitable X-ray illumination sources include rotating anode sources, fixed anode sources, particle accelerator sources, microfocus sources, laser generated plasma sources, liquid metal jet sources, gas jet/capillary/cell sources, Compton inverse scattering sources (ICS), compact storage ring sources (CSR), Electrical Discharge Produced Plasma (DPP) sources, High Harmonic Generation (HHG) sources, a HHG source with a gain cavity (HHG+), and soft x-ray laser sources.

Suitable X-ray illumination sources are described in U.S. Patent Publication No. 2019/0215940 , U.S. Patent Publication No. 2016/0249442 , U.S. Patent Publication No. 2016/0128171 , U.S. Patent Publication No. 2015/0076359 , U.S. Patent Publication No. 2015/0008335 , U.S. Patent Publication No. 2014/0306115 and U.S. Patent Publication No. 2014/0246607 , each of which is incorporated herein by reference in its entirety.

In some embodiments, the illumination source 110 is a wiggler/undulator synchrotron radiation source (SRS). An exemplary wiggler/undulator SRS is disclosed in U.S. Patent Nos. 8,941,336 and 8,749,179 described, the contents of which are incorporated herein by reference in their entirety.

In some embodiments, illumination source 110 is an electron beam source configured to bombard solid, liquid, or gaseous targets to stimulate x-ray radiation. Methods and systems for producing high brightness liquid metal X-ray illumination are disclosed in U.S. Patent No. 7,929,667 , issued April 19, 2011 to KLA-Tencor Corp., which is incorporated herein by reference in its entirety.

In some embodiments, the illumination source 110 is a laser produced plasma (LPP) light source. In some of these embodiments, the LPP light source includes any of the following emitter materials: xenon, krypton, argon, neon, nitrogen, alcohol, water. In general, the selection of a suitable LPP target material is optimized for brightness in resonant SXR regions. For example, plasma emitted by krypton offers high brightness at the silicon K-edge. In another example, xenon-emitted plasma provides high brightness over the SXR region, e.g. B. 80-3000 eV. As such, xenon is a good choice as an emitting material when broadband SXR illumination is desired.

The choice of LPP target material can also be optimized for reliable light source operation with long lifetime. Noble gas target materials such as xenon, krypton and argon are inert and can be reused in a closed loop with minimal or no decontamination process. An exemplary SXR illumination source is described in US Patent Publication No. 2019/0215940, the entire content of which is incorporated herein by reference in its entirety.

In some embodiments, a suitable illumination source is broadband. However, in some other embodiments, a suitable illumination source is not broadband, but rather includes multiple discrete wavelengths of radiation (e.g., an HHG source). In some of these embodiments, the reflectivity for each diffraction order includes multiple images, one for each discrete wavelength. In some embodiments, the periodic target is provided with multiple adjacent harmonics generated by an HHG source and a set of discrete points on the detector's photosensitive surface converge into a larger image.

A low divergence (e.g., less than 1 milliradian) illumination source is preferred to generate wavelength-resolved signal information as described herein. A low divergence illumination source is advantageous in some measurement applications (e.g. measuring 3D grids). Although a high divergence source can be used, it may require additional optical elements in the optical path from the illumination source to the detector to obtain wavelength-resolved signal information. This adds additional cost, complexity and photon loss to the metrology system.

In some embodiments, a broadband source that emits soft x-rays along with light at longer wavelengths (e.g., deep UV, vacuum UV, visible light, or IR) is used as the illumination source of the metrology system.

The x-ray illumination source 110 produces x-ray emission over a source area with finite lateral dimensions (i.e., non-zero dimensions orthogonal to the beam axis). In one aspect, the source area of illumination source 110 is characterized by a lateral dimension of less than 20 microns. In some embodiments, the source face is characterized by a lateral dimension of 10 microns or less. In some embodiments, the source face is characterized by a lateral dimension of 5 microns or less. A small source size enables a small target area on the sample to be illuminated with high brightness, improving measurement precision, accuracy, and throughput based on measurements of small metrology targets. In some embodiments, a small size (<5 microns in diameter) of the illumination source enables a scanning metrology system with submicron resolution.

The X-ray detector 119 collects the X-rays 118 scattered from the sample 101 and produces output signals 135 indicative of characteristics of the sample 101 that are sensitive to the incident X-rays according to a WR-SXR measurement modality. In some embodiments, scattered X-rays 118 are collected by X-ray detector 119 while sample positioning system 140 positions and orients sample 101 to generate angle-resolved scattered X-rays. In some embodiments, signal information about the uniformity of the sample is obtained by detecting signals at different locations across the sample 101 .

In general, any suitable type of x-ray detector can be used to perform WR-SXR measurements as described herein. Exemplary detectors include a charge-coupled device (CCD), a gas-electron multiplier (GEM), a microstrip proportional counter, a gas-filled proportional counter, a cadmium telluride (CdTe) detector, a pixel array detector (PAD) , an avalanche photodiode (APD), a PIN diode array, a photodiode array, a photomultiplier tube (PMT), a multichannel plate together with a CCD detector, a complementary metal oxide semiconductor (CMOS) detector, a scintillator together with a high-speed CMOS detector, a CMOS active pixel sensor (APS), etc.

In some embodiments, a WR-SXR system includes one or more high dynamic range (eg, greater than 10 ⁵ ) photon counting detectors. In some embodiments, the x-ray detector resolves one or more x-ray photon energies and generates signals for each x-ray energy component indicative of properties of the sample. In this way, the x-ray photon interactions within the detector are differentiated in terms of energy in addition to pixel position and count rate. In some embodiments, the x-ray photon interactions are discriminated by comparing the energy of the x-ray photon interaction to a predetermined upper threshold and a predetermined lower threshold. In one embodiment, this information is communicated via outputs 135 to computer system 130 for further processing and storage.

In another aspect, a WR-SXR system is used to determine properties of a sample (e.g., structural parameter values) based on wavelength-resolved signal information at one or more non-zero diffraction orders of scattered light. As in 1 As shown, the metrology tool 100 includes a computer system 130 that is used to acquire signals 135 generated by the detector 119 and to determine properties of the specimen based at least in part on the acquired signals.

In some examples, WR-SXR based metrology involves determining the dimensions of the sample by inverse solving a predefined measurement model with the measured data. The measurement model includes a few (on the order of ten) adjustable parameters and is representative of the geometry and optical properties of the sample and the optical properties of the measurement system. The inverse solution method includes, but is not limited to, model-based regression, tomography, machine learning, or any combination thereof. In this way, target profile parameters are estimated by solving for values of a parameterized measurement model that minimize errors between the measured scattered X-ray intensities and the modeled results.

It is desirable to make measurements over large ranges of wavelength, angle of incidence, and angle of azimuth in order to increase the precision and accuracy of the measured parameter values. This approach reduces correlations between parameters by expanding the number and variety of datasets available for analysis.

Measurements of diffracted radiation intensity are collected as a function of illumination wavelength, the angle of incidence of the x-rays relative to the wafer surface normal, or a combination thereof. Wavelength-resolved signal information contained in the multiple diffraction orders is typically unique for each model parameter considered. Thus, X-ray scattering provides estimation results for values of parameters of interest with small errors and reduced parameter correlation.

In one aspect, the metrology tool 100 includes a wafer chuck 103 that fixedly supports the wafer 101 and is coupled to the sample positioning system 140 . Sample positioning system 140 is configured to actively position sample 101 in six degrees of freedom with respect to illumination beam 114 . In one example, computer system 130 transmits command signals (not shown) to sample positioning system 140 indicating the desired position of sample 101 . In response, the sample positioning system 140 generates command signals to the various actuators of the sample positioning system 140 to achieve the desired positioning of the sample 101.

In some examples, measurements are made over a range of incidence angles, azimuth angles, and locations on the wafer to provide different illumination and coverage angles that are optimized to improve measurement performance.

In some embodiments, X-ray optics shape and direct X-ray radiation from illumination source 110 onto sample 101. In some examples, X-ray optics collimate or focus the X-ray beam onto measurement region 102 of sample 101 with a divergence of less than 1 milliradian using multi-layer X-ray optics. In some embodiments, the x-ray optics include one or more x-ray collimating mirrors, x-ray stops, x-ray stoppers, refractives X-ray optics, diffractive optics such as zone plates, Schwarzschild optics, Kirkpatrick-Baez optics, Montel optics, Wolter optics, specular X-ray optics such as ellipsoidal mirrors, polycapillary optics such as hollow capillary X-ray waveguides, multilayer optics or multilayer systems or any combination thereof. Further details are described in US Patent Publication No. 2015/0110249, the entire content of which is incorporated herein by reference.

7 12 illustrates an embodiment of a WR-SXR metrology tool 200 for measuring properties of a sample in another embodiment. As in 7 shown, focusing optics 111 focus source radiation onto a metrology target located on sample 101 . The finite lateral dimension of the source results in a finite spot size 102 on the target defined by the rays 116 coming from the edges of the source and any beam shaping provided by the beam slots 112 and 113.

In some embodiments, the focusing optics 111 include elliptically shaped optical focusing elements. in the in 7 shown embodiment, the magnification of the focusing optics 111 is approximately one in the center of the ellipse. As a result, the illumination spot size projected onto the surface of the sample 101 is approximately the same size as the illumination source, adjusted for beam broadening due to the nominal grazing incidence angle (e.g., 1-45 degrees).

In another aspect, focusing optics 111 collects source emission and selects one or more discrete wavelengths or spectral bands and focuses the selected light onto sample 101 at grazing incidence angles in the 1-45 degree range.

The nominal grazing angle of incidence is selected to achieve a desired penetration of the metrology target in order to maximize the signal information content while remaining within the bounds of the metrology target. The critical angle of hard X-rays is very small, but the critical angle of soft X-rays is significantly larger. As a result of this additional measurement flexibility, WR-SXR measurements penetrate deeper into the structure and are less sensitive to the exact value of the grazing incidence angle.

In some embodiments, the focusing optics 111 include gradual multilayers that select desired wavelengths or wavelength ranges for projection onto the sample 101 . In some examples, the focusing optics 111 includes a gradual multi-layer structure (e.g., layers or coatings) that selects a wavelength and projects the selected wavelength onto the sample 101 over a range of angles of incidence. In some examples, the focusing optics 111 includes a gradual multilayer structure that selects a range of wavelengths and projects the selected wavelengths onto the sample 101 over an angle of incidence. In some examples, the focusing optics 111 includes a gradual multilayer structure that selects a range of wavelengths and projects the selected wavelengths onto the sample 101 over a range of angles of incidence.

Graduated multilayer optics are preferred to minimize light loss that occurs when single layer grating structures are too deep. In general, multilayer optics select reflected wavelengths. The spectral bandwidth of the selected wavelengths optimizes the flux provided to the sample 101 and the information content in the measured diffraction orders, and avoids degradation of the signal by angular dispersion and diffraction peak overlap at the detector. Gradual multilayer optics are also used to control divergence. The angular divergence at each wavelength is optimized for the flux and minimal spatial overlap at the detector.

In some examples, graded multilayer optics select wavelengths to enhance the contrast and information content of diffraction signals from specific material interfaces or structural dimensions. For example, the selected wavelengths can be chosen to span element-specific resonance ranges (e.g., silicon K-edge, nitrogen, oxygen K-edge, etc.). Additionally, in these examples, the illumination source can also be tuned to maximize flux in the selected spectral range (eg, HHG spectral tuning, LPP laser tuning, etc.).

In some embodiments, reflective multilayer optics based on an Nb ₂ O ₅ mirror are used. 13 14 shows a graph 145 illustrating the reflectivity 146 of a Nb ₂ O ₅ mirror as a function of illumination beam energy. As in 13 shown, reflectivity of 85% or more is achieved over a wide range of x-ray energies. In some versions tion forms, Nb ₂ O ₅ mirrors are advantageous when used in combination with a broadband X-ray source.

In a further aspect, the ranges of wavelengths, AOI, azimuth or any combination thereof projected onto the same measurement area are adjusted by actively positioning one or more mirror elements of the focusing optics 111 . As in 7 As shown, computer system 130 transmits command signals 137 to actuator system 115, causing actuator system 115 to adjust the position, orientation, or both, of one or more of the optical elements of focusing optics 111 to achieve the desired ranges of wavelengths, AOI , azimuth, or any combination thereof.

In general, the angle of incidence is chosen to optimize penetration and absorption of the illuminating light by the metrology target to be measured. In many examples, multilayer structures are measured and the angle of incidence is selected to maximize signal information associated with the desired layers of interest. In the overlay metrology example, the wavelength(s) and angle(s) of incidence are chosen to maximize the signal information resulting from the interference between the scattering from the previous layer and the current layer. In addition, the azimuth angle is also selected to optimize the signal information content. In addition, the azimuth angle is chosen to ensure angular separation of the diffraction peaks at the detector.

In another aspect, a WR-SXR metrology system (e.g., a metrology tool 200) includes one or more beam slits or apertures to shape the illumination beam 114 incident on the sample 101 and selectively block a portion of the illumination light that would otherwise would illuminate a metrology target to be measured. One or more beam slots define the beam size and shape such that the X-ray illumination spot fits within the area of the metrology target to be measured. In addition, one or more beam slits define the divergence of the illumination beam to limit the overlap of diffraction orders on the detector.

7 12 illustrates a beam divergence control slit 112 located in the optical path between the focusing optics 111 and the beam shaping slit 113. FIG. The beam divergence control slit 112 limits the divergence of the illumination applied to the sample to be measured. Beam shaping slit 113 is located in the beam path between beam divergence control slit 112 and sample 101 . The beam shaping slit 113 further shapes the incident beam 114 and selects the illumination wavelength(s) of the incident beam 114 . The beam-shaping slit 113 is located in the beam path just before the sample 101. In one aspect, the slits of the beam-shaping slit 113 are in close proximity to the sample 101 to minimize the increase in spot size of the incident beam due to beam divergence defined by the finite source size.

In some embodiments, beam-forming slot 113 includes multiple, independently actuated beam-forming slots. In one embodiment, beam-forming slot 113 includes four independently actuated beam-forming slots. These four beam-shaping slits effectively block a portion of the incident beam and produce an illumination beam 114 with a box-shaped illumination cross-section.

Beam shaping slot 113 slots are constructed of materials that minimize scattering and effectively block incident radiation. Exemplary materials include single crystal materials such as germanium, gallium arsenide, indium phosphide, etc. Typically, the slot material is cleaved along a crystallographic direction, rather than sawed, to minimize scattering across structure boundaries. In addition, the slit is oriented with respect to the incident beam such that the interaction between the incident radiation and the internal structure of the slit material produces minimal scattering. The crystals are attached to each slit holder made of high-density material (e.g. tungsten) to completely block the X-ray beam on one side of the slit.

In another aspect, a WR-SXR metrology system as described herein uses one or more mechanisms to control the energy of the illumination beam. In general, illumination beam energies are selected to ensure adequate penetration of x-rays into the particular sample to be measured. In some examples, lower penetrating beam energies are chosen to measure parameters closer to the surface. In these examples, the illumination beam energies only probe the structure at the surface without penetrating deep into the structure. In In some examples, beam energies with greater penetration are selected to measure parameters deeper in the structure to be measured. In some examples, a combination of low and high penetration energies is chosen to distinguish surface structure parameters from deeper structure parameters.

In some embodiments, illumination beam energies are selected with an illumination source 110 that is tunable over a wide range of energies. In these embodiments, the illumination source itself emits illumination energies in the desired area(s). In some embodiments, illumination source 110 is an LPP light source that is controlled by computer system 130 to maximize flux in one or more selected spectral ranges. The laser peak intensity at the target material controls the plasma temperature and thus the spectral range of the emitted radiation. Laser peak intensity is varied by adjusting pulse energy, pulse width, or both. In one example, a pulse width of 100 picoseconds is suitable for generating SXR radiation. As in 1 As shown, computer system 130 transmits command signals 136 to illumination source 110 that cause illumination source 110 to adjust the spectral range of the wavelengths emitted by illumination source 110 . In one example, the illumination source 110 is an LPP light source, and the LPP light source adjusts pulse duration and/or pulse frequency and/or target material composition to realize a desired spectral range of wavelengths emitted by the LPP light source.

In some other embodiments, illumination beam energies are selected by one or more optical elements in the optical path between the illumination source and the sample to be measured. In some embodiments, the focusing optics 111 are selected to focus the illumination beam onto the sample to be measured in the desired beam energy range(s). In some embodiments, a beam energy filter 150 (in 7 shown) in the beam path between the illumination source and the sample to be measured. The beam energy filter transmits the desired beam energy range(s) to the sample to be measured and absorbs beam energies outside of the desired beam energy range(s).

8th 12 shows a representation of an illumination beam 114 passing through the beam energy filter 150 in one example. As in 8th As shown, the wavelength spectrum 152 of the incoming illumination beam 114 contains a large number of wavelength peaks. However, after passing through the beam energy filter 150, the wavelength spectrum 153 of the transmitted illumination beam 114 contains four distinct wavelength peaks.

9 15 is a graph 155 showing the transmission curve 156 of a beam energy filter 150 made from layers of boron and tin about 0.2 microns thick deposited on a Kapton substrate. As in 9 As shown, such a beam energy filter transmits beam energies in a range of approximately 140 eV to 190 eV and blocks beam energies outside of this band.

In another aspect, the incident illumination beam of a WR-SXR metrology system is controlled to have a relatively high divergence in a direction transverse to the incident illumination beam and a relatively low divergence in a second direction transverse to the incident illumination beam, orthogonal to the first direction . In this way, the spatial spread across the active surface of the detector in the high divergence direction is orthogonal to the spatial spread across the active surface of the detector in the low divergence direction. The spatial spread over the active surface of the detector in the direction of high divergence is dominated by the angle of incidence due to the relatively high divergence. In contrast, the spatial spread across the active surface of the detector in the direction of low divergence is dominated by the wavelength dispersion within each diffraction order, as described above. In this way, each non-zero diffraction order contains signal information about the structure to be measured due to spectral reflectance (in the direction of low divergence) and angular reflectance (in the direction of high divergence).

In some embodiments, the focusing optics of a WR-SXR system projects an image of the illumination source onto the sample to be measured, with a reduction of at least five (i.e. a magnification factor of 0.2 or less) in a direction transverse to the incident illumination beam and no magnification in a second direction transverse to the incident illumination beam orthogonal to the first direction. In some embodiments, a WR-SXR system as described herein uses an SXR illumination source having a source area defined by a lateral dimension of 20 microns or less (ie, the source size is 20 microns or less), with a low output divergence (e.g., about 1 milliradian or less) in any direction across the illumination beam. In some embodiments, focusing optics are used with a reduction factor of at least five (i.e., projects an image of the source onto the wafer that is five times smaller than the size of the source) in a first direction across the beam and no magnification in a second direction across the incident illumination beam orthogonal to the first direction. In this example, the incident illumination beam is projected onto a sample with an incident illumination spot size of twenty microns or less in the second direction and four microns or less in the first direction. In addition, the incident illumination beam is projected onto the sample with an incident illumination beam divergence of 1 milliradian or less in the second direction and 5 milliradian or less in the first direction.

10 FIG. 3 illustrates an embodiment of a WR-SXR metrology tool 300 in another embodiment. Equally numbered items that appear in 10 are analogous to those shown with reference to FIG 1 and 7 have been described. As in 10 As shown, the focusing optic 111 is an elliptical optical element with a curvature in one dimension. The focusing optics 111 is arranged with respect to the illumination source 110 and the sample 101 such that the distance A between the illumination source 110 and the focusing optics 111 is significantly greater than the distance B between the focusing optics 111 and the sample 101. In some embodiments, this is Ratio of A/B at least five. In some embodiments, the ratio of A/B is at least ten. This leads to a reduction of the illumination source on the sample 101 by the factor A/B. In one embodiment, the size of the illumination source 110 is approximately 10 microns and the focusing optics 111 are arranged such that A/B is ten. The beam divergence of the illumination beam emanating from illumination source 110 is approximately 0.5 milliradians in each direction across the illumination beam. In this embodiment, the illumination spot size projected onto the sample 101 is about 1 micron in the cross-beam direction, which is subject to demagnification, and about 10 microns in a second cross-beam direction and orthogonal to the first direction, which is not subject to demagnification. In addition, the incident illuminating beam is projected onto the sample with an incident illuminating beam divergence of approximately 0.5 milliradians in the second direction and 5 milliradians in the first direction.

11 Figure 14 shows a plot 141 of scattered radiation 118 incident on the active surface of detector 119, measured under the illumination conditions described in 10 are shown for single wavelength illuminating light. More precisely shows 11 the reflected beam 118A of the 0th order, diffracted radiation 118C corresponding to the -1 diffraction order, diffracted radiation 118E corresponding to the -2 diffraction order, diffracted radiation 118G corresponding to the -3 diffraction order and diffracted radiation 1181 corresponding to the -4 diffraction order. As in 11 As shown, the single wavelength present in the illuminating beam is diffracted by the periodic target 102 into each of the diffraction orders. There is very little spatial spread in the wavelength direction in the non-zero diffraction orders because the illuminating light contains only one wavelength and the beam divergence in that direction is relatively small (e.g., 0.5 milliradians). However, in the direction orthogonal to the wavelength direction, there is significant spatial spread over the angular range in all diffraction orders since the beam divergence in this direction is relatively high (e.g. 5 milliradians).

12 shows a plot 142 of scattered radiation 118 incident on the active surface of the detector 119, measured under the in 10 illustrated lighting conditions, for broadband illumination light. More precisely shows 12 the reflected beam 118A of the 0th order, diffracted radiation 118C corresponding to the -1 diffraction order, diffracted radiation 118E corresponding to the -2 diffraction order, diffracted radiation 118G corresponding to the -3 diffraction order and diffracted radiation 1181 corresponding to the -4 diffraction order. As in 12 As shown, the different wavelengths present in the illumination beam diffract from the periodic target 102 at different angles within each of the non-zero diffraction orders. Thus, the wavelength range λ _RANGE present in the illumination beam 114 is spatially spread in the y-direction for each of the non-zero diffraction orders. There is considerable wavelength spatial spread in the non-zero diffraction orders because the illuminating light contains several different wavelengths. Also, the beam divergence in this direction is relatively small (e.g., 0.5 milliradians), so the wavelength information present in the y-direction is not significantly affected by angular information. However, in the x-direction, orthogonal to the wavelength direction, there is significant spatial spreading over the angular range in all diffraction orders, since the beam divergence in this direction is relatively high (e.g. 5 milliradians). Thus, measurements at multiple wavelengths and with relative high beam divergence across the beam in one direction and relatively low beam divergence in a second direction across the beam orthogonal to the first direction provide both wavelength and angular signal information associated with the target to be measured.

US Patent Publication No. 2019/0017946 describes a polychromatic soft x-ray reflectometer system that generally uses incident illumination with relatively high divergence and is incorporated herein by reference in its entirety. However, such systems do not provide wavelength-resolved diffracted signals as described herein.

In general, the x-ray collection path between the sample to be measured and the detector of a WR-SXR metrology system can include any combination of elements used in the illumination path as described above.

In some embodiments, slits are used that block one or more diffraction orders. In one embodiment, a metallic beam stopper is used to block the zero order reflection.

In some embodiments, a spatial attenuator is located in the collection path to selectively attenuate a portion of the light associated with one or more diffractive orders (e.g., 0th order) but not other orders. In this way, all orders are measured simultaneously in the same dynamic range on the detector.

In general, the aforementioned optical elements placed in the illumination path, collection path, or both allow independent control of target size, photon flux, and beam shape for each measurement.

In another further aspect, measurement performance is improved by flowing one or more liquid materials or one or more gaseous materials onto the target to be measured to increase the contrast between the measured materials. A further description of these techniques is given in U.S. Patent Nos. 10,281,263 , 10,041,873 and 10,145,674 provided, the contents of which are hereby incorporated by reference in their entirety. In some embodiments, a vapor injection system provides a flow of gas containing a fill material in a vapor phase to the structure to be measured during illumination of the structure. A portion of the fill material is condensed onto the structure in the liquid phase. The portion of fill material fills at least a portion of a space between one or more geometric features of the structure.

In general, according to the systems and methods described herein, the target to be measured includes any periodic or semi-periodic structure in any step of a semiconductor manufacturing process.

In some embodiments, a WR-SXR metrology system as described herein is used to measure periodic metrology targets. For example shows 16A a metrology target 160 having a periodic grid structure with a pitch P. In another aspect, however, a WR-SXR metrology system as described herein is used to measure decimated metrology targets that exhibit both periodicity and aperiodicity. A decimated metrology target is a metrology target that includes an array of nominally periodic unit cells, and one or more cells of the nominally periodic array are deleted, shifted, or structurally modified at programmed or random locations within the array. For example shows 16B a metrology target 161 with a nominally periodic lattice structure of pitch P. However, beyond that, certain ribs of the lattice structure are not present in the metrology target 161. As a result, the angular distribution of scattering from the metrology target 161 during the measurement shows both periodic properties, resulting in localized diffraction peaks, and aperiodic behavior, also known as diffuse scattering.

In general, the diffuse scattering distribution between Bragg peaks is increased by randomly or programmed erasing elements of a nominally periodic unit cell array. The angular distribution of the diffuse intensity is proportional to the square of the structure factor. When depleted metrology targets are used, the intensity of the Bragg peaks decreases, but more pixels contain non-zero information content as the scattered light is spread over more pixels. Because model-based measurements can use information from all pixels, the overall increase in the information content of the measurement improves measurement precision and accuracy. In general, the Bragg peak intensity decreases as the proportion of erased cells increases. The desired decimation of the metrology target maximizes the overall information content of the measurement. In some examples, decimated metrology targets resolve an ambiguity that arises in cases where the structure factor of a metrology target is zero at a large subset of Bragg peak locations (e.g., a square wave at a 50% duty cycle). A WR-SXR metrology system can be used to measure a depleted metrology target in a single wavelength sequential mode of operation or in a multiple wavelength simultaneous mode of operation.

In some embodiments, a metrology target includes a general or specific aperiodicity selected to maximize signal information and thus minimize acquisition time. Design rules for standard logic cell arrays place primitive elements on a fixed grid and tightly control pattern density variations. Logical structure metrology focuses on achieving a high-precision estimate of average feature size and separation in a local area. Occupancy and periodicity are not of interest as these aspects are well controlled in the lithography process. A metrology target for logical structures optimizes the intensity distribution in such a way that the leakage flux is increased in angular ranges that contain a high information content with regard to the desired feature parameter set. In one example, a metrology target includes a border region to enhance the information content of diffraction through a central region.

In another further aspect, a WR-SXR metrology system uses multiple detectors. In some embodiments, one or more diffraction orders are collected by a first detector and other diffraction orders are collected by another detector.

14 FIG. 4 shows a WR-SXR metrology system 400 in another embodiment. As in 14 As shown, the active surface of detector 170 is in the ray path of non-zero diffraction orders, and the active surface of detector 171 is in the ray path of zero diffraction orders. in the in 14 In the embodiment shown, detector 170 includes an aperture that is transparent or semi-transparent, or a gap that allows the 0th diffraction order to pass to detector 171 . As in 14 As shown, detected signals 172 generated by detector 170 and detected signals 173 generated by detector 171 are communicated to computer system 130 .

In some embodiments, detector 170 is configured to measure x-ray wavelengths and detector 171 is configured to measure x-ray wavelengths, ultraviolet wavelengths, visible wavelengths, infrared wavelengths, or any combination thereof. in the in 14 In the embodiment shown, detector 171 is located within vacuum chamber 123. This embodiment is suitable for measurement configurations involving detection of radiation by detector 171, including soft X-rays. However, in some other embodiments, the detector 171 is located outside of the vacuum chamber 123. These embodiments are suitable for measurement configurations involving detection by the detector 171 of radiation other than soft X-rays (e.g., longer wavelengths such as ultraviolet, visible, infrared, etc.).

In another aspect, the position of a detector of a WR-SXR metrology system is actively controlled to capture radiation reflected from the target to be measured. In some embodiments, computer system 130 transmits control commands (not shown) to actuators (not shown) coupled to detector 119 that cause the active surface of detector 119 to be tilted or translated with respect to the light collected.

In some embodiments, WR-SXR enables measurements on design rule targets since the illumination wavelength(s) are shorter than the period of the structures being measured. This offers a significant advantage over existing technology where measurements are made on targets larger than the design rule targets. Using WR-SXR wavelengths enables target design in process design rules, i. H. no "non-zero offsets".

A metrology target for WR-SXR measurements can include one-dimensional periodic arrays or two-dimensional periodic arrays. Parameters of interest measured by WR-SXR include, but are not limited to, dimensional information about a sample (e.g. layer thicknesses, lattice heights, critical dimensions, sidewall angles, overlay, etch placement errors) and material information (e.g. material composition) .

In some embodiments, the illumination source 110 is an LPP light source with a source size of 10 microns or less, and the focusing optics 111 have a demagnification factor of about 10 up. This allows the WR-SXR metrology tool 300 to focus illuminating light on a metrology target with dimensions of 1-2 microns. By focusing the incident illumination light to an illumination spot size of 1-2 microns, the WR-SXR metrology tool 300 allows measurement of critical dimension targets and overlay targets located in the die rather than relying on larger metrology targets in the wafer scribe line areas.

The ability to measure targets as small as 1-2 microns reduces the wafer area dedicated to specialized metrology targets. In addition, the ability to measure targets as small as 1-2 microns allows direct measurement of device structures instead of dedicated metrology targets. Direct measurement of device structures eliminates target-to-device error. This significantly improves the measurement quality. In addition, measurements of in-die targets allow characterization of the parameter variation within the die. Example parameters of interest include critical dimensions, overlay, and edge placement errors such as endline shortening, line-to-contact spacing, etc.

In some embodiments, X-ray illumination source 110, focusing optics 111, slits 112 and 113, or any combination thereof are maintained in the same atmospheric environment (e.g., gas purge environment) as sample 101. However, in some embodiments, the optical path length between and within any of these elements is long, and x-ray scattering and absorption in air contribute to the noise and signal attenuation of the image on the detector. Therefore, in some embodiments, x-ray illumination source 110, and/or focusing optics 111, and/or slits 112 and 113 are maintained in a localized vacuum environment. in the in 7 In the embodiment shown, illumination source 110, focusing optics 111, and slits 112 and 113 are maintained in a controlled environment (e.g., vacuum) within evacuated flight tube 117. Illumination beam 114 passes through window 120 at the end of flight tube 117 before striking sample 101 .

Similarly, in some embodiments, the optical path length between sample 101 and detector 119 (ie, the collection path) is long and x-ray scattering and absorption in air contributes to noise and attenuation of the image on the detector. Therefore, in preferred embodiments, a significant portion of the length of the collection beam path between sample 101 and detector 119 is maintained in a localized vacuum environment separated from the sample (e.g., sample 101) by a vacuum window (e.g., vacuum window 124). is. In some embodiments, x-ray detector 119 is maintained in the same localized vacuum environment as the optical path portion between sample 101 and detector 119. For example, as shown in FIG 7 As shown, the vacuum chamber 123 maintains a localized vacuum environment surrounding the detector 119 and a significant portion of the optical path portion between the sample 101 and the detector 119.

In some other embodiments, x-ray detector 119 is maintained in the same atmospheric environment (e.g., gas purge environment) as sample 101 . This can be beneficial to remove heat from the detector 119. However, in these embodiments, it is preferable to maintain a significant portion of the optical path portion between the sample 101 and the detector 119 in a localized vacuum environment within a vacuum chamber.

In some embodiments, the entire optical system, including the sample 101, is kept under vacuum. In general, however, the cost associated with maintaining the sample 101 in vacuum is high due to the complexity associated with the design of the sample positioning system 140.

In another further aspect, the computer system 130 is configured to generate a structural model (e.g., a geometric model, a material model, or a combined geometry and material model) of a measured structure of a sample, generate a WR-SXR response model, including at least one geometric parameter from the structural model, and to be solved for at least one sample parameter value by performing a fitting analysis of WR-SXR measurement data with the WR-SXR response model. The analysis machine is used to compare the simulated WR-SXR signals with measurement data and thus enables the determination of geometric and material properties such as the electron density of the sample. in the in 1 In the embodiment shown, computer system 130 is configured as a model building and analysis engine configured to implement the model building and analysis functionality described herein.

15 12 is a diagram illustrating an example model building and analysis engine 180 implemented by computer system 130. FIG. As in 15 As shown, the modeling and analysis engine 180 includes a structural modeling module 181 that generates a structural model 182 of a measured structure of a sample. In some embodiments, the structural model 182 also includes material properties of the sample. The structure model 182 is received as input to the WR-SXR response function building module 183 . The WR-SXR response function formation module 183 generates a WR-SXR response function model 184 based at least in part on the structural model 182. The fit analysis module 185 compares the modeled WR-SXR response to the corresponding measured data to determine both geometric and material properties of the sample determine.

definiert werden.In some examples, fitting modeled data to experimental data is accomplished by minimizing a chi-square value. For example, for WR-SXR measurements, a chi-square value can be used as $${\chi }_{\mathrm{<figure-callout\; id="2"\; label="S\; X\; R"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">S</figure-callout>}XR}^2=\frac{1}{N_{SXR}}{\displaystyle {\sum }_j^{N_{SXR}}\frac{{\left(S_j^{SXRmO\mathrm{i.e}el}\left({\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">v</figure-callout>}}_1,...,v_L\right)-S_j^{SXRexpe\mathrm{right}iment}\right)}^2}{{\sigma }_{SXR,\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">j</figure-callout>}}^2}}$$

To be defined.

die gemessenen WR-SXR-Signale 126 im „Kanal“ j bedeutet, wobei der Index j einen Satz von Systemparametern wie Beugungsordnung, Energie, Winkelkoordinate usw. beschreibt. $S_j^{SXRmodel}\left(v_1,\dots ,v_L\right)$

bedeutet das modellierte WR-SXR-Signal S_j für den „Kanal“ j, ausgewertet für einen Satz von Struktur-(Ziel-)Parametern (v₁, ... , v_L), wobei diese Parameter Geometrie (CD, Seitenwandwinkel, Overlay usw.) und Material (Elektronendichte usw.) beschreiben. ${\sigma }_{SXR,j}^2$

ist die Unsicherheit, die dem j-ten Kanal zugeordnet ist. N_SXR ist die Gesamtzahl der Kanäle in der Röntgenmetrologie. L ist die Anzahl der Parameter, die das Metrologieziel charakterisieren.Whereby $S_j^{SXRmO\mathrm{i.e}elexpe\mathrm{right}iment}$

means the measured WR-SXR signals 126 in "channel" j, where the subscript j describes a set of system parameters such as diffraction order, energy, angular coordinate, etc. $S_j^{SXRmO\mathrm{i.e}el}\left({\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">v</figure-callout>}}_1,...,v_L\right)$

means the modeled WR-SXR signal S _j for the “channel” j evaluated for a set of structural (target) parameters (v ₁ , ... , v _L ), where these parameters are geometry (CD, sidewall angle, overlay, etc.) and material (electron density, etc.). ${\sigma }_{SXR,\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">j</figure-callout>}}^2$

is the uncertainty associated with the jth channel. N _SXR is the total number of channels in X-ray metrology. L is the number of parameters characterizing the metrology target.

ausgedrückt werden, wobei V_SXR die Kovarianzmatrix der WR-SXR-Kanalunsicherheiten ist und T die Transponierung bezeichnet.Equation (2) assumes that the uncertainties associated with different channels are uncorrelated. In examples where the uncertainties associated with the different channels are correlated, a covariance between the uncertainties can be calculated. In these examples, a chi-square value for WR-SXR measurements can be used as $$\begin{array}{l}{\chi }_{SXR}^{2}X=\frac{1}{N_{SXR}}{\left({\overrightarrow{S}}_j^{SXRmO\mathrm{i.e}el}\left({\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">v</figure-callout>}}_1,...,v_M\right)-{\overrightarrow{S}}_j^{SXRexpe\mathrm{right}iment}\right)}^T{V}_{SXR}^{-1}({\overrightarrow{S}}_j^{SXRmO\mathrm{i.e}el}\left({\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">v</figure-callout>}}_1,...,v_M\right)-\\ {\overrightarrow{S}}_j^{SXRexpe\mathrm{right}iment})\end{array}$$

where V _SXR is the covariance matrix of the WR SXR channel uncertainties and T denotes the transpose.

optimiert.In some examples, the fit analysis module 185 solves for at least one sample parameter value by performing fit analysis on WR-SXR measurement data 135 with the WR-SXR response model 184 . In some examples is $X_{\mathrm{<figure-callout\; id="2"\; label="S\; R\; X"\; filenames="DE112020004109T5\_0009.png,DE112020004109T5\_0011.png"\; state="\{\{state\}\}">S</figure-callout>}RX}^2$

optimized.

As described above, fitting WR-SXR data is achieved by minimizing chi-square values. However, in general, customization of WR-SXR data can be achieved through other functions.

In another further aspect, the computer system 130 is configured to train an input-output model (e.g., a neural network model, a signal response metrology model, etc.) that maps WR-SXR measurement data to values of one or more parameters of interest that characterize the structure to be measured (e.g. a geometric parameter describing the structure to be measured). In addition, the computer system 130 is configured to use the input-output model to estimate values of parameters of interest based on WR-SXR measurement data.

WR-SXR data can be analyzed using a range of data fitting and optimization techniques and technologies including: libraries, fast reduced order models, regression, machine learning algorithms such as neural networks and support vector machines (SVM), dimensionality reduction algorithms, e.g. B. PCA (principal component analysis), ICA (independent component analysis) and LLE (local linear embedding), sparse representation like Fourier or wavelet transform, Kalman filters, algorithms to promote matching of same or different tool types and others.

WR-SXR data can also be analyzed by algorithms that do not involve modeling, optimization and/or fitting, e.g. US Patent Publication No. 2015/0204664 and U.S. Patent Publication No. 2016/0216197 by Bringoltz et al., the contents of which are incorporated herein by reference in their entirety.

Analysis of WR-SXR measurement data is beneficial for any type of WR-SXR technology that offers sensitivity to geometric and/or material parameters of interest. Sample parameters can be deterministic (e.g. CD, SWA, etc.) or statistical (e.g. rms sidewall roughness level, roughness correlation length, etc.) as long as appropriate models are used to describe the WR-SXR beam interaction with the sample.

In general, the computer system 130 is configured to access model parameters in real time using Real-Time Critical Dimensioning (RTCD), or it can access libraries of pre-computed models to obtain a value from at least one sample parameter value associated with associated with sample 101. In general, any form of CD machine can be used to assess the difference between a sample's assigned CD parameters and CD parameters associated with the measured sample. Exemplary methods and systems for calculating sample parameter values are set forth in U.S. Patent No. 7,826,071 , issued November 2, 2010 to KLA-Tencor Corp., the entirety of which is incorporated herein by reference.

In some examples, the modeling and analysis engine 180 improves the accuracy of the measured parameters through any combination of sideways-coupling analysis, forward-coupling analysis, and parallel analysis. Side-linkage analysis refers to taking multiple data sets from different regions of the same sample and passing common parameters determined from the first data set to the second data set for analysis. Feedforward analysis refers to taking datasets from different samples and passing common parameters to subsequent analyzes using a stepwise, exactly copying, parameter feedforward approach. Parallel analysis refers to the parallel or simultaneous application of a nonlinear fitting methodology to multiple data sets where at least one common parameter is coupled during fitting.

Multiple tooling and structure analysis refers to a forward-coupling, sideways-coupling, or parallel analysis based on regression, a lookup table (ie, "library" matching), or other fitting method for multiple data sets. Exemplary methods and systems for multiple tool and structure analysis are in the U.S. Patent No. 7,478,019 , issued January 13, 2009 to KLA-Tencor Corp., which is incorporated herein by reference in its entirety.

In another further aspect, an initial estimate of values of one or more parameters of interest is determined based on WR-SXR measurements performed at a single orientation of the incident x-ray beam with respect to the metrology target. The initial estimated values are implemented as starting values of the parameters of interest for a regression of the measurement model with measurement data collected from WR-SXR measurements at multiple orientations. In this way, an accurate estimate of a parameter of interest is determined with relatively little computational effort, and by implementing this accurate estimate as a starting point for a regression over a much larger data set, a refined estimate of the parameter of interest is obtained with less overall computational effort.

In another aspect, metrology tool 100 includes a computer system (e.g., computer system 130) configured to implement the beam steering functionality described herein. in the in 7 In the embodiment shown, the computer system 130 is configured as a beam controller operable to control any illumination characteristics, such as intensity, divergence, spot size, polarization, spectrum, and positioning of the incident illumination beam 114.

As in 7 As shown, computer system 130 is communicatively coupled to detector 119 . Computer system 130 is configured to receive measurement data 135 from detector 119 . In one example, the measurement data 135 includes an indication of the measured response of the sample (ie, diffraction order intensities). Based on the distribution of the measured response on the surface of the detector 119, the location and area of incidence of the illumination beam 114 on the sample 101 is determined by the computing system 130. In one example, pattern recognition techniques are applied by computer system 130 to determine the location and area of incidence of illumination beam 114 on sample 101 based on measurement data 135 . In some examples, computer system 130 transmits command signals 136 to x-ray illumination source 110 to select the desired illumination wavelength. In some examples, computer system 130 transmits command signals 137 to actuator subsystem 115 to redirect x-ray emission to achieve a desired beam direction. In some examples, computer system 130 transmits command signals 138 and 139 to beam-forming slots 112 and 113, respectively, that cause beam-forming slots 112 and 113 to change beam spot size and select illumination wavelengths such that the incident illumination beam 114 is provided with the desired beam spot size, orientation, and/or arrives at the sample 101 at the desired wavelength(s). In one example, command signals 138 and 139 cause actuators associated with slots 112 and 113 to change position to reshape incident beam 114 to a desired shape and size and to select desired wavelengths. In some examples, computer system 130 transmits command signals 151 to beam energy filter 150 that cause beam energy filter 150 to filter out unwanted wavelengths from the spectrum of illumination beam 114 . In some other examples, computer system 130 transmits a command signal to wafer positioning system 140 to position and orient sample 101 such that incident illumination beam 114 arrives at the desired location and angular orientation with respect to sample 101.

In another aspect, WR-SXR measurement data is used to generate an image of a measured structure based on the measured intensities of the detected diffraction orders. In some embodiments, a WR-SXR response function model is generalized to describe scattering from a generic electron density mesh. Fitting this model to the measured signals while constraining the modeled electron densities in this mesh to enforce continuity and sparse edges provides a three-dimensional image of the sample.

Although geometric, model-based, parametric inversion is preferred for WR-SXR measurement-based critical dimension metrology (CD metrology), WR-SXR measurement data is useful to identify and correct model errors when the measured sample is of deviates from the assumptions of the geometric model.

In some examples, the image is compared to structural features estimated by a geometric, model-based parametric inversion of the same scatterometry measurement data. Deviations are used to update the geometric model of the measured structure and improve measurement performance. The ability to converge to an accurate parametric measurement model is particularly important when measuring integrated circuits to control, monitor and troubleshoot their manufacturing process.

In some examples, the image is a two-dimensional (2-D) map of electron density, absorbance, complex refractive index, or a combination of these material properties. In some examples, the image is a three-dimensional (3-D) map of electron density, absorbance, complex refractive index, or a combination of these material properties. The map is created using relatively few physical constraints. In some examples, one or more parameters of interest, such as critical dimension (CD), sidewall angle (SWA), overlay, edge placement error, pitch pitch, etc. are estimated directly from the resulting map. In some other examples, the map is useful for debugging the wafer process when the sample geometry or materials deviate outside the range of expected values considered by a parametric structure model used for model-based CD measurements. In one example, the differences between the map and a representation of the structure predicted by the parametric structure model according to its measured parameters are used to update the parametric structure model and improve its measurement performance. Further details are described in US Patent Publication No. 2015/0300965, the entire content of which is hereby incorporated by reference. Further details are described in US Patent Publication No. 2015/0117610, the entire contents of which are hereby incorporated by reference.

In another aspect, the modeling and analysis engine 180 is used to generate models for combined x-ray and optical metrology analysis. For example, in some examples, optical simulations are based on rigorous coupled wave analysis (RCWA), where Maxwell's equations are solved to calculate optical signals such as reflectivities for different polarizations, ellipsometric parameters, phase change, etc.

Values of one or more parameters of interest are determined based on a combined fitting analysis of the detected X-ray diffraction order intensities at the multiple different angles of incidence and detected optical intensities with a combined, geometrically parameterized response model. The optical intensities are measured by an optical metrology tool, which may or may not be mechanically integrated into an X-ray metrology system, such as that in 1 system 100 shown. Further details are provided in U.S. Patent Publication No. 2014/0019097 and US Patent Publication No. 2013/0304424, the contents of each of which are incorporated herein by reference in their entirety.

It should be appreciated that the various steps described throughout the present disclosure may be performed by a single computer system 130 or, alternatively, by a multiple computer system 130 . In addition, various subsystems of system 100, such as sample positioning system 140, may include a computer system suitable for performing at least a portion of the steps described herein. Therefore, the above description should not be interpreted as a limitation of the present invention, but only as an illustration. Furthermore, the one or more computer systems 130 may be configured to perform one or more other steps of any of the method embodiments described herein.

In addition, computer system 130 may be communicatively coupled to x-ray illumination source 110, beam-forming slits 112 and 113, focusing optics actuator system 115, sample positioning system 140, and detector 119 in any manner known in the art. For example, the one or more computer systems 130 may be connected to computer systems associated with x-ray illumination source 110, beam shaping slits 112 and 113, focusing optics actuator system 115, sample positioning system 140, or detector 119. In another example, x-ray illumination source 110, beam shaping slits 112 and 113, focusing optics actuator system 115, sample positioning system 140, and detector 119 may be directly controlled by a single computer system coupled to computer system 130.

Computer system 130 may be configured to receive and/or acquire data or information from the system's subsystems (e.g., x-ray illumination source 110, beam-forming slits 112 and 113, focusing optics actuator system 115, sample positioning system 140, detector 119, and the like) through a transmission medium that may include wired and/or wireless portions. In this manner, the transmission medium may serve as a data link between computer system 130 and other subsystems of system 100.

The computing system 130 of the metrology system 100 may be configured to receive and/or acquire data or information (e.g., measurement results, modeling inputs, modeling results, etc.) from other systems through a transmission medium, including wired and/or wireless portions can. In this way, the transmission medium can serve as a data link between the computer system 130 and other systems (e.g., embedded memory in the metrology system 100, external memory, or external systems). For example, computer system 130 may be configured to receive measurement data (e.g., signals 135) from a storage medium (i.e., memory 132 or 190) via a data connection. For example, spectral results obtained using detector 119 may be stored in a permanent or semi-permanent storage device (e.g., memory 132 or 190). The measurement results can be imported from an integrated memory or from an external storage system. In addition, computer system 130 may send data to other systems over a transmission medium. For example, sample parameter values 186 determined by computer system 130 may be stored in a permanent or semi-permanent storage device (e.g., memory 190). Measurement results can be exported to another system.

The computer system 130 may be a personal computer system, a mainframe computer system, a workstation, an image computer, a parallel processor, or any other art known devices include, but is not limited to. In general, the term "computer system" can be broadly defined to include any device with one or more processors that execute instructions from a storage medium.

Program instructions 134 implementing methods such as those described herein may be transmitted over a transmission medium such as a wire, cable, or wireless transmission link. As for example in 1 As shown, program instructions stored in memory 132 are transmitted to processor 131 via bus 133 . Program instructions 134 are stored on a computer-readable medium (e.g., memory 132). Exemplary computer-readable media includes read-only memory, random access memory, magnetic or optical disk, or magnetic tape.

17 Figure 5 illustrates a method 500 suitable for implementation by the metrology systems 100, 200, 300 and 400 of the present invention. In one aspect, it is recognized that data processing blocks of method 500 may be performed via a pre-programmed algorithm executed by one or more processors of computer system 130. While the following description is presented in the context of metrology systems 100, 200, 300, and 400, it is recognized herein that the particular structural aspects of metrology systems 100, 200, 300, and 400 are not limiting and should be interpreted as illustrative only.

In block 501, a set of soft x-rays is generated from an x-ray illumination source. Soft x-rays include multiple illumination wavelengths within a photon energy range of 10 electron volts to 5,000 electron volts. The soft X-ray beam is directed onto a metrology target fabricated on a semiconductor wafer as an X-ray illumination beam incident on the semiconductor wafer at a nominal grazing angle of incidence between 1 and 45 degrees.

At block 502, a first amount of x-ray radiation scattered into multiple different diffraction orders by the metrology target in response to the incident x-ray illumination beam is detected.

In block 503, a first plurality of measurement signals are generated. Each of the first plurality of measurement signals is indicative of the detected amount of x-ray radiation at a different location on an active surface of a first detector. The first plurality of measurement signals is also indicative of a particular wavelength of the plurality of illumination wavelengths diffracted to a particular one of the plurality of different diffraction orders.

In block 504, a value of a parameter of interest that characterizes the metrology target is determined based on the plurality of measurement signals.

In some embodiments, scatterometry measurements as described herein are implemented as part of a manufacturing process tool. Examples of manufacturing process tools include, but are not limited to, lithographic exposure tools, film deposition tools, implant tools, and etch tools. In this way, the results of a WR-SXR analysis are used to control a manufacturing process. In one example, WR-SXR measurement data collected from one or more targets is sent to a manufacturing process tool. The WR-SXR measurement data is analyzed as described herein and the results are used to adjust the operation of the manufacturing process tool to reduce errors in the fabrication of semiconductor structures.

Scatterometry measurements as described herein can be used to determine properties of a variety of semiconductor structures. Exemplary structures include, but are not limited to, FinFETs, low-dimensional structures such as nanowires or graphene, sub-10 nm structures, lithographic structures, through-substrate vias (TSVs), memory structures such as DRAM, 4F2 DRAM, FLASH, MRAM and high aspect ratio memory structures. Exemplary structural properties include, but are not limited to, geometric parameters such as line edge roughness, line width roughness, pore size, pore density, sidewall angle, profile, critical dimension, pitch, thickness, overlay, and material parameters such as electron density, composition, grain structure, morphology, stress, strain, and element identification. In some embodiments, the metrology target is a periodic structure. In some other embodiments, the metrology target is aperiodic.

In some examples, measurements of critical dimensions, thickness, overlay, and material properties of high aspect ratio semiconductor structures including, but not limited to, spin-transfer-torque random access memory (STT-RAM), three-dimensional NAND memory (3D -NAND) or vertical NAND memory (V-NAND), dynamic random access memory (DRAM), three-dimensional FLASH memory (3D-FLASH), resistive random access memory (Re-RAM), and phase change random access memory (PC-RAM) with WR-SXR - metrology systems as described herein.

As described herein, the term "critical dimension" includes any critical dimension of a structure (e.g., bottom critical dimension, middle critical dimension, top critical dimension, sidewall angle, lattice height, etc.), a critical dimension between any two or more structures ( e.g. distance between two structures) and a shift between two or more structures (e.g. overlay shift between overlapping lattice structures etc.). Textures can include three-dimensional textures, patterned textures, overlay textures, and so on.

As described herein, the term "critical dimension application" or "critical dimension measurement application" encompasses any critical dimension measurement.

As described herein, the term “metrology system” encompasses any system used, at least in part, to characterize a sample in any aspect, including critical dimension applications and overlay metrology applications. However, such terms do not limit the scope of the term “metrology system” as described herein. Additionally, the metrology systems described herein may be configured to measure patterned wafers and/or unpatterned wafers. The metrology system can be configured as an LED inspection tool, edge inspection tool, backside inspection tool, macro inspection tool, or multimode inspection tool (with data from one or more platforms simultaneously), and any other metrology or inspection tool that benefits from the metrology techniques described herein.

Described herein are various embodiments for a semiconductor processing system (e.g., an inspection system or a lithography system) that may be used to process a sample. The term "sample" is used herein to refer to a wafer, reticle, or any other sample that can be processed (e.g., printed or inspected for defects) by means known in the art.

As used herein, the term "wafer" generally refers to substrates formed from a semiconductor or non-semiconductor material. Examples include, but are not limited to, monocrystalline silicon, gallium arsenide, and indium phosphide. Such substrates are commonly found and/or processed in semiconductor manufacturing facilities. In some cases, a wafer may include only the substrate (i.e., the bare wafer). Alternatively, a wafer may include one or more layers of different materials formed on a substrate. One or more layers formed on a wafer may be "patterned" or "unpatterned". For example, a wafer may include a multitude of dies that have repeatable pattern features.

A “reticle” can be a reticle at any stage of a reticle manufacturing process or a completed reticle that may or may not be released for use in a semiconductor manufacturing facility. A reticle or "mask" is generally defined as a substantially transparent substrate on which substantially opaque areas are formed and configured in a pattern. For example, the substrate may comprise a glass material such as amorphous SiO ₂ . A reticle may be placed over a photoresist covered wafer during an exposure step of a lithography process so that the pattern on the reticle can be transferred to the photoresist.

One or more layers formed on a wafer can be patterned or unpatterned. For example, a wafer may include multiple dies, each having repeatable pattern features. The formation and processing of such layers of material can ultimately result in finished devices. Many different types of devices can be formed on a wafer, and as used herein the term wafer is intended to encompass a wafer on which any type of device known in the art is fabricated.

In one or more example embodiments, the described functions may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or stored on a computer-readable medium one or more instructions or codes are transmitted. Computer-readable media includes both computer storage media and communications media, including any media that enables the transfer of a computer program from one place to another. A storage medium can be any available medium that can be accessed by a general purpose or special purpose computer. By way of example and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage, or other magnetic storage device, or any other medium that can be used to carry desired program code means in the form of instructions or data structures or to be stored and accessed by a general purpose or special purpose computer or processor. Also, any compound is properly referred to as a computer-readable medium. For example, if the Software is transmitted from a website, server, or other remote source over coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwave included in the definition of medium. Disc and disc as used herein include compact disc (CD), laser disc, XRF disc, digital versatile disc (DVD), floppy disc and Blu-ray disc, where discs typically reproduce data magnetically while discs reproduce data optically with laser reproduce. Combinations of the above should also be included within the scope of computer-readable media.

Although certain specific embodiments have been described above for instructional purposes, the teachings of this patent document have general applicability and are not limited to the specific embodiments described above. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

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Claims (22)

Metrology system comprising: an x-ray illumination source configured to generate an amount of soft x-ray radiation comprising multiple illumination wavelengths within a photon energy range of 10 electron volts to 5,000 electron volts, the amount of soft x-ray radiation being directed at a metrology target fabricated on a semiconductor wafer, as an x-ray illumination beam, the is incident on the semiconductor wafer at a nominal grazing incidence angle of between 1 and 45 degrees; a first detector disposed in an optical path of a first quantity of x-ray radiation scattered from the metrology target into a plurality of different diffraction orders in response to the incident x-ray illumination beam, the first detector being configured to generate a first plurality of measurement signals, each indicative of the detected amount of x-ray radiation at a different location on the first detector, each of the first plurality of measurement signals being indicative of a particular one of the plurality of illumination wavelengths diffracted to a particular one of the plurality of different diffraction orders; and a computer system configured to determine a value of a parameter of interest characterizing the metrology target based on the first plurality of measurement signals. metrology system claim 1 , further comprising: a second detector disposed in an optical path of a second quantity of x-ray radiation scattered from the metrology target into one or more different diffraction orders in response to the incident x-ray illumination beam, the second detector being configured to detect a second generate a plurality of measurement signals each indicative of the detected amount of x-ray radiation at a different location on the second detector, each of the second plurality of measurement signals being indicative of the one or more different diffraction orders, the computer system being further configured to determine the value of the parameter of interest that characterizes the metrology target based on the first and second plurality of measurement signals. metrology system claim 2 , wherein the second amount of X-ray radiation comprises radiation in one of the following spectral ranges: a deep ultraviolet spectral range, a vacuum ultraviolet spectral range, a visible spectral range and an infrared spectral range. metrology system claim 1 , further comprising: one or more X-ray illumination optical elements arranged in an illumination optical path between the X-ray illumination source and the semiconductor wafer, wherein the one or more X-ray illumination optical elements focus the amount of soft X-ray radiation onto the semiconductor wafer as an X-ray illumination beam directed onto the semiconductor wafer with a nominal grazing incidence angle between 1 and 45 degrees. metrology system claim 1 , wherein the X-ray illumination source is a laser-based High Harmonic Generation (HHG) illumination source. metrology system claim 1 , further comprising: a beam energy filter located in an optical path between the x-ray illumination source and the semiconductor wafer, the beam energy filter transmitting x-ray illumination within a desired beam energy range and absorbing x-ray illumination outside the desired beam energy range. metrology system claim 1 , wherein the X-ray illumination source emits the quantity of soft X-rays with a beam divergence of less than one milliradian. metrology system claim 1 , further comprising: an optical reduction element in an optical path between the X-ray illumination source and the semiconductor wafer, wherein the optical reduction element focuses the X-ray illumination beam onto the semiconductor wafer with a magnification factor of 0.2 or less in a first direction transverse to the X-ray illumination beam and with a magnification factor of 0.9 or more in a second direction across the x-ray illumination beam orthogonal to the first direction. metrology system claim 1 wherein the x-ray illumination source is further configured to emit radiation in one of the following spectral ranges: a deep ultraviolet spectral range, a vacuum ultraviolet spectral range, a visible spectral range, and an infrared spectral range. metrology system claim 1 wherein the x-ray illumination source has an illumination source area characterized by a maximum extension dimension of less than 50 microns. metrology system claim 1 , where the parameter of interest is one of the following: an overlay error, a critical dimension, an edge placement error. metrology system claim 1 , further comprising: a vapor injection system that provides a gas flow to the metrology target during illumination of the metrology target that contains a fill material in a vapor phase. metrology system claim 1 , wherein the X-ray illumination source is adjusted to produce the amount of soft X-ray radiation including a desired photon energy range. metrology system claim 1 , further comprising: one or more x-ray illumination optical elements arranged in an illumination optical path between the x-ray illumination source and the semiconductor wafer, wherein the one or more x-ray illumination optical elements focus the amount of soft x-ray radiation onto the semiconductor wafer as an x-ray illumination beam emitted at multiple angles of incidence , is incident on the semiconductor wafer at several wavelengths and with several azimuth angles. metrology system Claim 14 wherein the one or more X-ray illumination optical elements are graded multilayer optical elements that select the multiple illumination wavelengths. Method comprising: Providing a quantity of soft X-ray radiation comprising multiple illumination wavelengths within a photon energy range of 10 electron volts to 5,000 electron volts, the quantity of soft X-ray radiation being directed at a metrology target fabricated on a semiconductor wafer as an X-ray illumination beam incident on the semiconductor wafer with a nominal grazing incidence angle between 1 and 45 degrees; detecting a first amount of x-ray radiation scattered into a plurality of different diffraction orders by the metrology target in response to the incident x-ray illumination beam; generating a first plurality of measurement signals, each of the first plurality of measurement signals being indicative of the detected amount of X-ray radiation at a different location on an active surface of a first detector, each of the first plurality of measurement signals being indicative of a particular wavelength of the plurality of illumination wavelengths diffracted to a specific diffraction order of the plurality of different diffraction orders; and determining a value of a parameter of interest characterizing the metrology target based on the first plurality of measurement signals. procedure after Claim 16 , further comprising: detecting a second amount of x-ray radiation scattered into one or more diffraction orders by the metrology target in response to the incident x-ray illumination beam; and generating a second plurality of measurement signals, each of the second plurality of measurement signals being indicative of the detected amount of x-ray radiation at a different location on an active surface of a second detector, each of the second plurality of measurement signals being indicative of the one or more diffraction orders, wherein the determining the value of the parameter of interest characterizing the metrology target is based on the first and second plurality of measurement signals. procedure after Claim 17 , wherein the second amount of X-ray radiation comprises radiation in one of the following spectral ranges: a deep ultraviolet spectral range, a vacuum ultraviolet spectral range, a visible spectral range and an infrared spectral range. procedure after Claim 17 , further comprising: filtering the X-ray illumination beam in an optical path between the X-ray illumination source and the semiconductor wafer. procedure after Claim 17 , further comprising: magnifying the X-ray illumination beam in a first direction transverse to the X-ray illumination beam by a magnification factor of 0.2 or less; and projecting the x-ray illumination beam onto the semiconductor wafer at a magnification factor of 0.9 or more in a second direction transverse to the x-ray illumination beam orthogonal to the first direction. Metrology system comprising: an x-ray illumination source configured to generate an amount of soft x-rays comprising multiple illumination wavelengths within a photon energy range of 10 electron volts to 5,000 electron volts, wherein the amount of soft x-rays is directed at a metrology target fabricated on a semiconductor wafer than at the semiconductor wafer incident X-ray illumination beam; a first detector disposed in an optical path of a first quantity of x-ray radiation scattered from the metrology target into a plurality of different diffraction orders in response to the incident x-ray illumination beam, the first detector being configured to generate a first plurality of measurement signals, each of the first plurality of measurement signals being indicative of the detected amount of x-ray radiation at a different location on the first detector, each of the first plurality of measurement signals being indicative of a particular wavelength of the plurality of illumination wavelengths diffracted to a particular one of the plurality of different diffraction orders; a second detector disposed in an optical path of a second quantity of x-ray radiation scattered from the metrology target into one or more different diffraction orders in response to the incident x-ray illumination beam, the second detector being configured to provide a second plurality of measurement signals generate each of the second plurality of measurement signals indicative of the detected amount of x-ray radiation at a different location on the second detector, each of the second plurality of measurement signals indicative of the one or more different diffraction orders; and a computer system configured to determine a value of a parameter of interest characterizing the metrology target based on the first and second plurality of measurement signals. metrology system Claim 21 , wherein the second quantity of X-ray radiation comprises radiation in one of the following spectral ranges: a deep ultraviolet spectral range, a vacuum ultraviolet spectral range, a visible spectral range and an infrared spectral range.

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